The present invention relates to optical instruments for developing a corrective ophthalmic prescription and, more particularly, to apparatuses and methods for subjectively refining a corrective prescription based on aberrations determined by a wavefront measuring device (WMD).
The eye is an optical system having several optical elements for focusing light rays representing images onto the retina within the eye. The sharpness of the images produced on the retina is a factor in determining the visual acuity of the eye. Imperfections within the lens and other components and material within the eye, however, may cause the light rays to deviate from the desired path. These deviations, referred to as aberrations, result in blurred images and decreased visual acuity. Hence, methods and apparatuses for measuring aberrations are used to aid in the correction of such problems.
One method of detecting aberrations introduced by the eye involves the determination of aberrations introduced into light rays exiting from the eye. An input beam of light focused into the eye to a point on the retina is reflected or scattered back out of the eye as a wavefront. The wavefront contains the aberrations introduced as the wavefront passes through the eye""s optical elements and exits the eye. By determining the propagation direction of discrete portions (i.e., samples) of this wavefront, the aberrations can be determined, thereby enabling the production of corrective lenses and/or performance of other corrective procedures that restore visual acuity.
FIG. 1 is an illustration of a prior art WMD 10 for measuring aberrations within a wavefront 100 and correcting aberrations. An input beam 102 generated by a radiation source 104 (e.g., a laser) is routed to an eye 106 by a beam splitter 108 where it is focused to a small spot 110 on the retina 112 within the eye 106. The wavefront 100 reflected from the spot 110 on the retina 112, which acts as a diffuse reflector, becomes aberrated as it passes through the lens and other components and materials within the eye 106. In an ideal eye, the wavefront 100 would be free of aberrations. In an imperfect eye 106, however, aberrations are introduced as the wavefront 100 passes out of the eye 106 and results in an imperfect wavefront containing aberrations.
On the return path, the wavefront 100 passes through the beam splitter 108 to a sensor 114 that includes, for example, a Hartman-Shack lenslet array 116 and an imaging device 118 containing a charge coupled device (CCD). A quarter-wave plate 120, positioned between the eye 106 and the beam splitter 108, is a known technique for manipulating the polarization of the input beam 102 going into the eye 106 and the wavefront 100 emanating from the eye 106 to allow the wavefront 100 to pass through the beam splitter 108 toward the wavefront sensor 114. Additional lenses 122 are positioned between the eye 106 and the wavefront sensor 114 to image the plane of the pupil of the eye 106 onto the wavefront sensor 114 with a desired magnification. Information detected by the wavefront sensor 114 is then processed by a processor 124 to determine the aberrations of the wavefront 100, which can be used to develop a corrective prescription for the eye 106.
While the WMD 10 depicted in FIG. 1 is able to determine aberrations introduced by the eye 106 with a high degree of accuracy, the development of a corrective prescription needs to be precisely tailored to a patient""s visual needs. In addition, vision correction involves a perceptual aspect (i.e., psychophysics) that cannot be captured with conventional WMDs. It is therefore desirable to obtain subjective feedback from the patient during the development of the corrective prescription. Accordingly, methods and apparatuses for subjectively refining corrective prescriptions based on aberrations determined by WMDs are needed. The present invention fulfills this need among others.
The present invention discloses methods and apparatuses for subjectively refining corrective prescriptions based on aberrations determined by WMDs. In the present invention, an image is altered to reflect the corrective prescription and presented to a patient. Feedback is received from the patient to vary the corrective prescription, and further alter the image, which is again presented to the patient for further feedback. This process is repeated until the image presented to the patient is acceptable to the patient. The corrective prescription at this point becomes the patient""s preferred corrective prescription.
One aspect of the present invention is a method for obtaining a preferred corrective prescription for an eye of a patient. The method includes measuring aberrations of a wavefront emanating from the eye, computing a proposed corrective prescription based on the measured aberrations, presenting to the patient an image altered to reflect the proposed corrective prescription, receiving feedback from the patient about the image altered to reflect the proposed corrective prescription, varying the proposed corrective prescription based on feedback from the patient, presenting to the patient an image altered to reflect the varied corrective prescription, and receiving feedback from the patient about the image altered to reflect the varied corrective prescription. The corrective prescription is then varied based on feedback from the patient and an image altered to reflect the varied corrective prescription is presented to the patient for feedback, repeatedly, to obtain the preferred corrective prescription.
Another aspect of the present invention is an apparatus for obtaining a preferred corrective prescription for an eye of a patient. The apparatus includes a WMD capable of measuring aberrations of the eye, a processor configured to determine a proposed corrective prescription including one or more components based on the measured aberrations, a display device to present an image reflecting the corrective prescription to the patient, and an input device capable of varying at least one of the one or more components based on feedback from the patient to obtain the preferred corrective prescription.